Add comprehensive unit tests for kubespy components

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This PR adds comprehensive unit tests to the kubespy project, which previously had no test coverage. The tests cover all major internal components and provide a solid foundation for future development and refactoring.

What's Added

Test Coverage by Package:

• k8sconfig - 100% coverage: Tests Kubernetes configuration creation and client config interface compliance
• k8sobject - 96.7% coverage: Tests ownership checking, pod conditions extraction, and container status parsing
• pods - 92.6% coverage: Tests ready/unready pod parsing from Kubernetes endpoints objects
• watch - 16.3% coverage: Tests watch options creation and object filtering logic
• cmd - 7.4% coverage: Tests object ID parsing functionality with proper error handling
• print - 1.1% coverage: Tests status event printing utility functions
• version - 100% of testable code: Tests version variable handling

Key Test Scenarios Covered:

• Edge cases and error conditions (invalid inputs, missing fields, malformed data)
• Valid input scenarios with expected outputs
• Type checking and validation for Kubernetes objects
• Configuration handling in various environments
• Object ownership relationships across different API versions
• Pod readiness state parsing from endpoints

Test Infrastructure:

• 7 new test files with 60+ individual test cases
• Proper mocking and isolation for external dependencies
• Comprehensive error case handling (e.g., missing kubeconfig in test environment)
• Table-driven tests for comprehensive scenario coverage

All tests pass successfully and the build remains functional. The test suite integrates with the existing Makefile test_all target and follows Go testing best practices.

Fixes #171.

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